Document Server@UHasselt
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Repository of the University of Hasselt containing publications in the fields of statistics, computer science, information strategies and material from the Institute for behavioural sciences.
Mostrando recursos 1 - 15 de 15
1.
Alternative gate dielectric materials - Van Elshocht, S.; HARDY, An; De Gendt, S.; Adelmann, D.; Brunco, D.; Caymax, M.; Conard, T.; Delugas, P.; Lehnen, P.; Shamiryan, D.; Vos, R.; Witters, P.; Zimmerman, P.; Meuris, M.; Heyns, M.
The semiconductor industry is facing the challenging task
of finding a candidate to replace silicon oxide, which has
been the CMOS gate dielectric of choice for more than 50
years. A material with a dielectric constant (k) higher
than SiO2 will allow making the dielectric thicker by a
factor of k/k(SiO2), hence lowering the gate current
leakage levels, and this without reduction of the
capacitance and thus performance.
2.
Alternative gate dielectric materials - Van Elshocht, S.; HARDY, An; De Gendt, S.; Adelmann, D.; Brunco, D.; Caymax, M.; Conard, T.; Delugas, P.; Lehnen, P.; Shamiryan, D.; Vos, R.; Witters, P.; Zimmerman, P.; Meuris, M.; Heyns, M.
The semiconductor industry is facing the challenging task
of finding a candidate to replace silicon oxide, which has
been the CMOS gate dielectric of choice for more than 50
years. A material with a dielectric constant (k) higher
than SiO2 will allow making the dielectric thicker by a
factor of k/k(SiO2), hence lowering the gate current
leakage levels, and this without reduction of the
capacitance and thus performance.
3.
Aqueous solution-gel preparation of ultrathin ZrO2 films for gate dielectric application - HARDY, An; Van Elshocht, S.; Adelmann, C.; Conard, T.; Franquet, A.; DOUHERET, Olivier; HAELDERMANS, Ilse; D'HAEN, Jan; De Gendt, S.; Caymax, M.; Heyns, M.; D'OLIESLAEGER, Marc; VAN BAEL, Marlies; MULLENS, Jules
Zirconia ultrathin films were deposited by aqueous chemical solution deposition, using citratoperoxo-Zr(IV) precursors with different citric acid content. The precursor synthesis, thermal decomposition and crystallization of oxide powders were studied. This showed an effect of the citric acid content in every stage. The precursors were applied for the deposition of uniform, ultrathin films (<30 nm thickness) as well. Tetragonal ZrO2 crystallized starting from 500 degrees C for thin films with a thickness of 10 nm. This was independent of the citric acid content in the precursor. The topography after annealing at 600 degrees C was also similar. However, annealing at...
5.
Monte Carlo analysis of error propagation in the potentiometric determination of equilibrium constants - GUEDENS, Wanda; MULLENS, Jules; VAN POUCKE, Lucien
The calculation of formation constants of metal complexes is an important and active area of modern solution chemistry. The precision with which these constants are calculated can be quantified by a Monte Carlo technique from realistic estimates of the experimental errors in (potentiometric) titration parameters. Moreover, having better estimates of the standard deviations, this capability of Monte Carlo analysis has potential implications for model selection.
A Matlab® program suite has been developed in order to quantify the statistical uncertainty on the optimized stability constants in complex models. The suite consists of a data generation program and a refinement program. The free...
6.
Fourier-Transform Photocurrent Spectroscopy for a fast and highly sensitive spectral characterization of organic and hybrid solar cells - VANDEWAL, Koen; GORIS, Ludwig; HAELDERMANS, Ilse; NESLADEK, Milos; HAENEN, Ken; WAGNER, Patrick; MANCA, Jean
Two modes of Fourier-Transform Photocurrent Spectroscopy (FTPS) are presented for a fast and sensitive determination of photocurrent spectra of organic and dye sensitized solar cells. Furthermore, FTPS allows to spectrally resolve sub-bandgap absorption phenomena in P3HT, in organic P3HT:PCBM bulk heterojunctions and in hybrid P3HT/TiO2 solar cells. The sub-bandgap absorption in the P3HT:PCBM blend is dominated by a band due to the formation of a ground-state charge-transfer complex between the polymer and PCBM. In P3HT/TiO2 junctions such a charge-transfer complex band is not observed. Long-lived light induced sub-bandgap states appear in pure P3HT and in P3HT/TiO2 junctions after irradiation with...
7.
Crystallization resistance of barium titanate zirconate ultrathin films from aqueous CSD: a study of cause and effect - HARDY, An; Van Elshocht, Sven; Knaepen, Werner; D'HAEN, Jan; Conard, Thierry; Brijs, Bert; Vandervorst, Wilfred; Pourtois, Geoffrey; Kittl, Jorge; Detavernier, Christophe; Heyns, Marc; VAN BAEL, Marlies; VAN DEN RUL, Heidi; MULLENS, Jules
Ultrathin BaZr0.8Ti0.2O3 films (t < 30 nm) on SiOx/Si substrates were obtained by means of aqueous chemical solution deposition (CSD). Though the precursor crystallized into cubic perovskite powder at 600 degrees C, ultrathin films only crystallized at 950 to 1000 degrees C, even after addition of excess Ba to compensate for loss of Ba. Films with thickness above 100 nm, on the other hand, crystallized readily around 650 degrees C. The crystallization is related to film thickness, affecting the crystallization activation energy, and to silicate formation by reaction with the substrate, exerting its largest influence in ultrathin films. Barium deficiency,...
8.
Morphology of water-based chemical solution deposition (CSD) lead titanate films on different substrates: Towards island formation - DE DOBBELAERE, Christopher; HARDY, An; D'HAEN, Jan; VAN DEN RUL, Heidi; VAN BAEL, Marlies; MULLENS, Jules
This study aims at the deposition of PbTiO3 (PT) islands prepared by a water-based chemical solution deposition (CSD). Two aqueous citrato-based PbTiO3 precursor solutions, either with or without peroxide, are deposited by spin coating. The effect of different substrates on the formation of separated grains or islands is examined. It is observed that spin coating of a 0.6 M precursor solution on a Pt(1 1 1)/IrO2/Ir/SiO2/Si substrate gives the best results towards island formation. For this substrate, crystallizations are carried out between 600 degrees C and 900 degrees C. A final crystallization at 800 degrees C results in the highest...
9.
Thermal behaviour of arsenic trioxide adsorbed on activated carbon - Cuypers, Frederic; DE DOBBELAERE, Christopher; HARDY, An; VAN BAEL, Marlies; Helsen, Lieve
The thermal stability and desorption of arsenic trioxide (As2O3) adsorbed on activated carbon (AC) was investigated as this phenomenon is expected to influence the arsenic release during low temperature pyrolysis of chromated copper arsenate (CCA) wood waste. Firstly, a thermogravimetric (TG) experiment with arsenolite, an allotropic form of As2O3, was performed. The sample starts to sublime at temperatures lower than 200,C with a sublimation peak temperature of 271 degrees C. Subsequently, TG experiments with samples of As2O3 adsorbed on AC revealed that only very little (max. 6 +/- 3 wt%) As2O3 was volatilised at temperatures below 280 degrees C, while...
11.
In pursuit of "super"high-k ternary oxides: aqueous CSD and material properties - HARDY, An; VAN ELSHOCHT, Sven; D'HAEN, Jan; DE GENDT, Stefan; VAN BAEL, Marlies K.; D'OLIESLAEGER, Marc; HEYNS, Marc; MULLENS, Jules
Important material properties of dielectric oxide films fabricated by aqueous chemical
solution deposition, such as crystallization, topography, contamination and interfacial layer were
evaluated and related to the films’ dielectric properties.
Functional ultrathin films (<20 nm thickness) of zirconia, barium zirconate and strontium
niobate were deposited. These films were all subjected to the same pyrolysis treatment, based on
the high similarity of their precursors’ thermal decomposition behavior. The evolution of the
chemical purity as a function of temperature and the effect of annealing on the interfacial SiO2
layer was studied by grazing angle ATR-FTIR. The crystallization behavior was dependent on
film thickness and composition as shown by high temperature...
12.
How stable are polymer: PCBM bulk heterojunction solar cells? - BERTHO, Sabine; HAELDERMANS, Ilse; SWINNEN, Ann; D'HAEN, Jan; LUTSEN, Laurence; MANCA, Jean; VANDERZANDE, Dirk
This paper investigates the thermal stability of organic bulk heterojunction solar cells, with a special focus on the thermal ageing of both photovoltaic parameters and morphology of the active layer. The photovoltaic parameters of a set of bulk heterojunction solar cells were determined by IV-characterization and their bulk morphology was investigated with transmission electron microscopy (TEM). A link could be made between the degradation of the short circuit current under a thermal treatment and the corresponding change in bulk morphology. A possible improvement of the thermal stability of bulk heterojunction solar cells is presented through the use of a polymer...
13.
Influence of thermal ageing on the stability of polymer bulk heterojunction solar cells - BERTHO, Sabine; HAELDERMANS, Ilse; SWINNEN, Ann; MOONS, Wouter; MARTENS, Tom; LUTSEN, Laurence; VANDERZANDE, Dirk; MANCA, Jean; Senes, Alessia; Bonfiglio, Annalisa
A new approach is presented in order to improve the thermal stability of polymer: [6-6]-phenyl C-61 butyric acid methyl ester (PCBM) bulk heterojunction solar cells. The central idea in this approach is the use of a polymer with high glass transition temperature (T-g), well above the normal operating temperatures of the devices. In this paper, a PPV-derivative with a T-g of 150 degrees C was used as an electron donor and the thermal stability of the obtained solar cells was compared with solar cells based on the reference material poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene] (MDMO-PPV) with a T-g of 45 degrees C. The...
14.
Study of interfacial reactions and phase stabilization of mixed Sc, Dy, Hf high-k oxides by attenuated total reflectance infrared spectroscopy - HARDY, An; Adelmann, C.; Van Elshocht, S.; VAN DEN RUL, Heidi; VAN BAEL, Marlies; De Gendt, S.; D'OLIESLAEGER, Marc; Heyns, M.; Kittl, J.A.; MULLENS, Jules
Grazing angle attenuated total reflectance Fourier transform infrared spectroscopy is applied to study ultrathin film Hf4+, Sc3+ and Dy3+ oxides, due to its high surface sensitivity. The (multi) metal oxides studied, are of interest as high-k dielectrics. Important properties affecting the permittivity, such as the amorphous or crystalline phase and interfacial reactions, are characterized. Dy2O3 is prone to silicate formation on SiO2/Si substrates, which is expressed in DyScO3 as well, but suppressed in HfDyOx. Sc2O3, HfScOx and HfO2 were found to be stable in contact with SiO2/Si. Deposition of HfO2 in between Dy2O3 or DyScO3 and SiO2, prevents silicate formation,...
15.
Structural and optical properties of DNA layers covalently attached to diamond surfaces - WENMACKERS, Sylvia; POP, SD; Roodenko, K; VERMEEREN, Veronique; WILLIAMS, Oliver; DAENEN, Michael; DOUHERET, Olivier; D'HAEN, Jan; HARDY, An; VAN BAEL, Marlies; Hinrichs, K.; Cobet, C; VAN DE VEN, Martin; AMELOOT, Marcel; HAENEN, Ken; MICHIELS, Luc; Esser, N.; WAGNER, Patrick
Label-free detection of DNA molecules on chemically vapor-deposited diamond surfaces is achieved with spectroscopic ellipsometry in the infrared and vacuum ultraviolet range. This nondestructive method has the potential to yield information on the average orientation of single as well as double-stranded DNA molecules, without restricting the strand length to the persistence length. The orientational analysis based on electronic excitations in combination with information from layer thicknesses provides a deeper understanding of biological layers on diamond. The pi-pi* transition dipole moments, corresponding to a transition at 4.74 eV, originate from the individual bases. They are in a plane perpendicular to the...
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